Electrode array for use in electrochemical cells

ABSTRACT

The invention features an electrode array ( 7 ) in which pairs of electrodes ( 1 ) are geometrically arranged so that the broadest faces of the exposed electrodes are not directly opposing to each other. Rather, the broadest facing surfaces of the electrodes in the array are parallel, adjacent, or offset at an angle. The electrode geometry of an electrode array of the invention permits electrodes to be in close proximity, thereby lowering series resistance, while minimizing the possibility for short circuits that can cause electrical leakage. An electrode array of the invention can be used in an electrochemical cell, such as a battery, e.g., a lithium battery, a capacitor, a flow-through capacitor, or a fuel cell.

REFERENCE TO PRIOR APPLICATION

This application is based on and claims priority from U.S. ProvisionalPatent Application Ser. No. 60/307,789, filed Jul. 25, 2001, herebyincorporated by reference in its entirety.

GOVERNMENT CONTRACT

This invention was funded under contract with the Army Research Office,under Contract No. DDAD 19-00-C-0448. The United States Government mayhave certain rights in the invention.

FIELD OF THE INVENTION

The field of the invention is electrodes for electrochemical cells.

BACKGROUND OF THE INVENTION

In electrochemical cells, such as capacitors, batteries, fuel cells, andflow-through capacitors, it is desirable to reduce series resistance andelectrical leakage, which waste energy. Normally, to reduce seriesresistance, it would be desirable place the electrodes close together.However, proximity is difficult to achieve with purely opposingelectrodes. In order to place the electrodes close together, forexample, closer than 0.03 inches (˜760 μm), the dielectric between themmust be thin, but this geometry has the undesirable effect of increasingthe electrical leakage. Moreover, where the electrochemical cell is aflow-through capacitor, thin dielectric spacers lead to a drop inpressure. Therefore, it is desirable to provide for a new and improvedelectrochemical cell with minimal series resistance and with lowelectrical leakage.

SUMMARY OF THE INVENTION

The invention features an electrode array in which pairs of electrodesare geometrically arranged so that the broadest faces of the exposedelectrodes are not directly opposed to each other. Rather, the broadestfacing surfaces of the electrodes in the array are parallel, adjacent,or offset at an angle. The electrode geometry of an electrode array ofthe invention permits electrodes to be in close proximity, therebylowering series resistance, while minimizing the possibility for shortcircuits that can cause electrical leakage.

The electrode array of the present invention may function as an anode,cathode, or as a stand-alone capacitor or electrochemical cell combiningcathodes and anodes in one sheet of material.

Electrodes may be formed as patterns of lines, dots, or other shapesplaced on, attached, or formed onto a substrate, including a conductivematerial, or, alternatively, a nonconductive sheet material. Theselines, dots, etc., may be formed in very thin layers and may be spacedvery close. An electrochemical cell, fuel cell, battery, capacitor, orflow-through capacitor is formed by the adjacent pairs or groups oflines and dots.

Thus, one aspect the invention features an array of electrodes, wherebythe broadest exposed electrode faces of the electrodes are adjacent toeach other. Alternatively, the broadest faces of the exposed electrodesare coplanar or offset at an angle, but not directly opposite to eachother, whether on the same sheet of a material containing both anodesand cathodes, or between separated anode sheets and cathode sheets. Thisminimizes the possibility for short circuits that cause leakage. Theelectric field comes up out of the anodes and curves back to thecathode. The electrodes of the array can be dots, shapes, or lines thatcan be recessed into the dielectric spacer as a further means ofprotecting against electrical leakage between them.

The electrode array of the present invention uses a geometricarrangement of parallel, adjacent, or offset electrodes in order tocreate capacitors, electrochemical cells, or flow-through capacitors. Adielectric insulator serves as a spacer between adjacent electrodes; thespacer may be a porous, nonporous, ion-permeable, ion-selective,membrane, or other dielectric material. Optionally, current collectorsare in electrical contact with the electrodes, either placed under, orembedded in, or sandwiched between, the electrodes.

The adjacent geometry of the electrodes within the electrode arrayreduces series resistance and leakage sufficiently that the distancebetween the anode and the cathode can be less than 0.03 inches, or canpreferably be reduced to 0.005 inches, or to less than 0.001 inches.Electrode materials in any shapes separated by insulating materials maybe manufactured with a narrow distance between adjacent electrodes,reduced to 1 micron or less, by using manufacturing methods commonlyused to print circuit boards in the semiconductor industry. Where it ispreferred to use a wider space between the electrodes, for example, over0.001 cm, manufacturing methods such as screen or other printing orcoating methods will suffice to manufacture the electrode array of thepresent invention.

The electrode array of the invention can be used in any type ofelectrochemical cell, such as capacitors, batteries, and fuel cells. Anelectrode array of the invention can be a used in a flow-throughcapacitor. Alternatively, an electrode array of the invention can beused in a lithium battery.

In one embodiment, the electrode array is comprised of dots, shapes, orlines that may be recessed into the spacer as a further means ofprotecting against electrical leakage between them. The broadest facesof the electrodes are offset from each other.

An additional advantage of the present invention is that the electrodearrays may be lines, dots, or any other shapes that can be arranged inpatterns with small distances between shapes or nonfacing or adjacentsurfaces of each pair of electrodes, for example, less than 3millimeters, thereby allowing construction of an electrode arraycontaining anode-cathode pairs within a single sheet of material.Therefore, the electrode array sheet may comprise anode-cathode pairs toact as an integrated capacitor, electrochemical cell, or flow-throughcapacitor. These electrode array sheets, containing one or moreanode-cathode pairs per sheet, may be stacked together in any geometryknown to prior art flow-through capacitors, electrochemical cells, waterfilters, batteries, or electronic capacitors.

In one embodiment, the electrode pattern of the present invention formsa two-dimensional electrode array. The electrode array may be used as adouble-layer capacitor, capacitor, flow-through capacitor, fuel cell, orany other electrochemical device. The thin electrodes, for example, lessthan 0.13 cm thick, and thin spacing, for example, less than 0.13 cmapart, of this array reduce leakage and ESR. Leakage is reduced becausethe broadest area of each electrode of an electrode pair is offset fromthe other electrode. Because the electrodes may be placed close togetherwithout generating electrical leakage, series resistance is reduced.Series resistance of less than 50 ohms/cm² of electrode array facingarea and leakage resistance of more than 30 ohms/cm² of electrode arrayfacing area can be achieved by the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a frontal illustration of an embodiment of an electrode arraythat includes two parallel electrodes and a spacer, optionally separatedby a current collector.

FIG. 1B is a cross-sectional view of the electrode array shown in FIG.1A.

FIG. 2 is an illustration of an electrode array in which adjacentconcentric electrodes are separated by a dielectric spacer.

FIG. 3 shows two of the concentric electrode arrays illustrated in FIG.2, separated by a flow spacer, which forms a flow path.

FIG. 4 shows a layered geometry for designing and manufacturing anelectrode array according to the present invention, where (A) is a basesupporting layer; (B) is a an insulating layer formed by forming apattern of dielectric spacer on the base substrate shown in (A); (C)shows a linear array of electrode material placed on top of the portionsof the substrate that remain exposed in layer (B); (D) shows an optionaladditional set of electrodes which are electrically insulated from theelectrodes deposited in (C); and (E) is a second current collectoroptionally placed against the electrode array shown in (D).

FIG. 5 shows an electrode array in which the electrodes may optionallyeither protrude from or be embedded in a substrate. The substrate mayoptionally be an insulating layer or current collector. The electrodesare coplanar and may have either underlying or overlying currentcollectors.

FIG. 6 shows an electrode array in which the electrodes are coplanar andadjacent to each other within the same sheet of material.

FIG. 7 illustrates two electrode arrays placed together.

FIG. 8 illustrates a flow channel formed by the misalignment of groovesbetween two electrode arrays.

FIG. 9 illustrates an alternative design of a flow-through capacitor orflow-through electrochemical cell utilizing an electrode array in aspiral-wound configuration.

DETAILED DESCRIPTION

The electrode array of the present invention may be used in double-layercapacitors; flow-through capacitors or electrochemical cells; solidpolymer electrolyte or nonelectrolyte-containing capacitors;nonelectrolytic, nonelectrolyte-containing, solidelectrolyte-containing, or in nondouble layer batteries or capacitors,by use of any conductive metal or material for the electrode, and use ofany dielectric material for the spacer, including ceramic, polymer,MYLAR® (MYLAR is a registered trademark of E.I. Du Pont De Nemours andCompany Corporation of Wilmington, Del.) sheet material, or any othermaterials commonly used to make film-type capacitors. Arrays ofelectrodes of the present invention may also be used for lithium storageor other intercalation battery devices, either combined with anelectrolyte or with a solid polymer electrolyte material.

A preferred embodiment of the present invention is the use of the arrayfor electrolyte-containing electrochemical cells and flow-throughcapacitors. Any carbon or carbon binder mixture known in the art indouble-layer capacitors may be used. Gel and hydrogel binders are alsoefficacious, including use of ion-permselective (i.e., selectivepermeability) or cross-linked, ion exchange, polyelectrolyte gels. Whereboth anodes and cathodes are included in the same sheet array material,the sheet itself may form an entire electrochemical cell or flow-throughcapacitor. These sheets may be stacked together in any geometry known toflow-through capacitors, batteries, or water filters, including spiralwound, pleated, stacked polygon, or disc. Where anode-cathode pairs arecontained within the same sheet of material, each sheet itself functionsas an electrochemical cell. In this way, anode and cathode pairs do notneed to be formed between two opposing layers or sheets. The spacingbetween adjacent anode-cathode electrode pairs within the same sheet maybe small, and no longer simultaneously depends upon the thickness of theflow spacer, as in prior art flow-through capacitors, electrochemicalcells, and flow-through electrochemical cells. The spacer does not needto do double duty as both an insulator, which requires thinness for lowseries resistance, and a flow channel, which has the oppositerequirements of open area. Therefore, when used in flow cells, such asflow-through capacitors and fuel cells, the spacing between opposingelectrode array sheets may be much thicker than the spacing betweensheet electrodes of prior art electrochemical cells. Because the sheetelectrodes of the present invention can constitute complete electriccells, unlike prior art electrochemical cells, the separation distancebetween sheet electrodes may be increased without substantiallyincreasing series resistance. For example, the facing surfaces of thesheet electrode or electrode array may be separated by flow spacers orspacers of greater than 0.002 cm thick, for example, up to 1.0 cm thickor more. No flow spacer at all may be used, in which case theelectrolyte, working fluid, or purification or concentration feed streammay be simply flowed past or over the electrode array. Where flowspacers are used, the cells may be made using any cartridge geometry,cartridge holders common to prior art flow-through capacitors, orelectrochemical cells, with the option that spacers between layers maybe replaced by holding the layers apart under tension, with shims orsupports placed more than 1.0 mm apart, or alternatively, the thickerspacers above may be used to achieve low pressure drops of less than 2kilograms per square centimeter and not significantly increase seriesresistance.

U.S. Pat. No. 6,110,354, issued Aug. 29, 2000, teaches electrode arraysused for electrochemical sensors, whereby the nonfaradaic, capacitancecomponent is minimized. An additional purpose of the present inventionis to maximize the nonfaradaic, capacitance component used in energygeneration, energy storage, or other electrochemical cells. This is doneby the selection of relatively high surface area electrode materials.For use in capacitors and many other electrochemical cells, a preferredembodiment of the present invention is use of electrode material with asurface area of over 10 square meters per gram B.E.T. For use incapacitors, certain batteries, and other electrochemical cells,electrode materials with a surface area of over 300 m² per gram arepreferred. Otherwise, U.S. Pat. No. 6,110,354 and the references citedtherein teach methods of manufacture and electrode array geometries thatmay be directly adapted to the present invention by the incorporation ofsaid relatively high surface area electrode materials. The presentinvention may make use of electrodes with the less than 100 micronspacing described in U.S. Pat. No. 6,110,354, or, may alternatively makeuse of wider electrodes with over 10 to 1000 times greater facing areaand spacing than described in U.S. Pat. No. 6,110,354. All the means offabricating and interconnecting electrodes, as well as the generalgeometry and method of making flow channels with or of the electrodesdescribed in U.S. Pat. No. 6,110,354 may be used in the presentinvention. Use of inert electrode materials, such as graphite, gold,platinum series metals, and any form of carbon, is particularlypreferred. However, for use in many batteries, electrochemicallyreactive metals, and other conductive compounds which form reversiblesurface area compounds or complexes may be preferentially used.

Another preferred form of the present invention is the selection ofelectrode array dimensions, whereby the distance between anode andcathode electrodes is less than the diffusion length of the electrolytesolute for a given charge cycle time.

The electrode array of the present invention may also be used foranalytical electrochemistry of any material present in the electrolyte,including organic, inorganic, or biological compounds.

FIG. 1A shows a frontal view of an electrode array 7 formed from twoelectrodes 1 that are in the shape of lines and are arranged inparallel. The electrodes 1 are separated by spacer 2, and optionallyseparated by a current collector 6. Optional lead means 5 connectalternating electrodes 1 into alternating arrays of anodes and cathodes.Lead means 5 may also be used to connect every two or more alternateelectrodes 1, or only the end electrodes 1, in order to form electrodesin series.

FIG. 1B is a cross-sectional view showing one electrode 1 line and itsunderlying optional current collector 6. This current collector 6 maytypically be metal or graphite, and the electrode 1 may typically be ahigh capacitance carbon held together with a binder, for use indouble-layer capacitors, flow-through capacitors, or electrochemicalcells, or, may be aluminum or other metal for use in solid polymerelectrolyte or nonelectrolyte-containing capacitors.

The electrode array 7 of FIG. 1 is formed by any manufacturing methodable to form patterns of adjacent lines or shapes, such as by coating,printing, extruding, coextruding, spraying, or electroplating theelectrodes 1 onto a spacer 2. Coating methods may include, but are notlimited to: dip, brush, knife, roll, airbrush, spray, extruded, print,cast, and strip coating.

FIG. 2 shows an electrode array 7 formed by adjacent concentric spiralor circle electrodes 1 sandwiching spacer or spacers 2. Thiscombination, with optional current collectors 6 that may underlie oroverlay the electrode layers, forms the electrode array 7 of the presentinvention. Current collectors 6 may be placed within or bisect electrodelayers, or form a sandwich with an electrode layer either to the sidesof the current collector 6, perpendicular to the sheet surface, or aboveand below the current collector 6, parallel to the sheet surface.

In FIG. 3, two of the concentric electrode arrays 7 depicted in FIG. 2are arranged for use in a flow-through capacitor or flow-electrochemicalcell. The electrode arrays 7 are separated by a flow spacer 3, whichforms a flow path 4 for the flow of fluid across the electrodes 1. Leads5 can connect to a source of power. Alternatively, leads 5 form a seriesconnection with another capacitor.

FIGS. 4A-4E show a stepwise process of arranging a layered geometry foran electrode array according to the present invention. In FIG. 4A, aplanar sheet is provided to serve as a base or supporting layer on whichto form the electrode array 7. In the embodiment shown, the supportinglayer is prepared from a planar sheet current collector 6, such as asheet of graphite or metal, either alone as a thin sheet, for example,under 0.15 cm thick, a foil sheet, e.g., a foil sheet of less than 0.03cm thick, or a conductive material coated on top of a support material,such as plastic, or MYLAR®, or the like.

In FIG. 4B, an insulating layer is deposited to form a dielectric spacer2. Dielectric spacer 2 can be formed onto the supporting substrate byprocesses known to those skilled in the art. Without limitation, thedielectric spacer 2 can be laced, coated, printed, embossed, engraved,machined, or attached on top of the base layer. This insulating layercan have a geometry of lines, as shown in here, or may be of alternativeshapes, such as dots, squares, stars, polygons, or circles.

In an alternative embodiment, the order of addition of materials used toform these two layers can be reversed. In this configuration (notshown), the substrate layer is formed from a sheet of a dielectricmaterial, on which is deposited a current collector material as thelayer analogous to that shown in FIG. 4B, as lines or other adjacentshapes on top of the supporting substrate.

FIG. 4C shows linear electrode material that has been placed on top ofthe exposed current collector lines of FIG. 4B. One method to do thiswould be to apply or wipe on a capacitance-containing or other electrodematerial, typically a carbon material mixed with a binder. Thiscapacitance material could, for example, fill grooves formed by exposedcurrent collector and flanking spacer layers. Excess can be washed orwiped off. In addition to printing methods of manufacture, variousmethods may be employed to apply this and other layers. For example, anylayer may be etched, deposited from a gas phase, roll coated, spincoated, dip coated, doctor bladed, coated, sprayed, stamped, orelectrocoated, electron beam manufactured, laser and microphotographically plotted, etched, or masked, electrochemically plated orreacted, or otherwise attached or placed upon the exposed currentcollector 6.

FIG. 4D shows an optional additional set of electrodes 1 which areelectrically insulated from the first set of electrodes 1, so that theymay be charged oppositely to these to form either anodes or cathodes.Electrodes 1 may be either anodes or cathodes. In order that theelectrodes 1 may comprise groupings of two or more that may formanode-cathode groups or pairs when placed opposite to each other, thepairs or groups of electrodes 1 must be made on top of insulating layer2. The anodes and cathodes do not have to be equal in number or size.They may optionally be equal in additive surface area if it is desirableas a means to improve function or balance the voltage. It may also bedesirable to connect all electrodes on a given current collector 6together, or to isolate or electrically insulate every other electrode1, or some lesser percentage, for example, {fraction (1/100)} of{fraction (1/10)}, spaced evenly throughout the electrode array 7. Inthis way, half or more of the electrodes 1 may be connected together toform an anode or cathode, and half or less of the remaining electrodesmay be connected together to form the oppositely-charged cathode oranode. To form a capacitor, more or less equal numbers of likeelectrodes 1, or different numbers of electrodes 1 representing equalamounts of capacitive material, should be used.

FIG. 4E is a second current collector 6 that may optionally besandwiched against the electrode array 7 shown in FIG. 4D in order toprovide current to subsets of electrodes 1. Preferably, however, acurrent collector 6 may be printed as lines on top of electrodes 1.These could be cross-connected by a perpendicular lead 5, as shown inFIG. 1.

Generally, the insulating layer is manufactured such that a pattern ofcurrent collector lines, dots, squares, stars, polygons, circles, anyother shapes shows through, is made on top of, or, is produced paralleland adjacent to, the insulating layer(s) 2, creating current collectorlayer(s) 6 with exposed faces. Photo masking, photo lithography, padprinting, screen or other forms of printing are one good ways to makethe structures shown in layers 4B, 4C, and 4D.

FIG. 5 is a cross-sectional schematic view of the electrode array 7shown in FIG. 4D. This shows that the optional current collector 6 mayeither be a continuous layer connecting electrodes 1 together, as shownin the top part of FIG. 1B, or may be arrayed along with the electrodes1 themselves in a discontinuous fashion, restricted on, within, or moreor less congruent with the electrodes 1, as shown in the bottom of FIG.5.

One preferred embodiment of the invention is shown in FIG. 6. Electrodes1 are both coplanar and adjacent within the same sheet of material.Current collectors 6 may underlie, be embedded in, or bisect a doubledelectrode layer, one on each side of the current collector 6.Insulating, dielectric, ionically-conducting or nonionic-conductingspacers 2 prevent electron leakage between electrodes 1, allowing anodeand cathode pairs to form. The anodes and cathodes may be connected inseries or in parallel, for example, as shown in FIG. 1.

FIG. 7 illustrates how two electrode arrays 7 can be placed together inorder to bracket a flow channel. A channel for fluid flow may be formedvia flow spacer 4 by use of an electrically-insulating, added spacermaterial or layer, or a pair of layers, including membranes, nonwoven,and woven materials (not shown) through which a fluid can flow, whichflow spacer 4 may be ionically conductive or not. Any layer mayoptionally be raised, protruded, or recessed above or below the otherlayers of the array surface, as shown, for the particular case ofelectrodes 1. Raised layers may be placed together on opposing electrodearray sheets to form a flow path 4.

As shown in FIG. 8, flow path 4 may be formed by either aligning ormisaligning of grooves, ridges, or bumps represented by any combination,either together or different, of the current collector 6, electrodes 1,or dielectric spacer 2, when put together to form flow paths 4 from twoelectrode arrays 7. As an example, two planar electrode arrays 7 areprepared. In the first array, either or both of electrodes 1 anddielectric spacers 2 can be formed on a substrate layer as a raisedlines, bumps, or the like. The second electrode array 7 is formed in alikewise manner, by forming electrodes 1, dielectric spacers 2, andoptionally, current collectors 6 as raised lines or other. When thesetwo arrays are put together, the lines or shapes are offset in order toform biplanar other flow channels, as shown in FIG. 8. Alternatively,any of the materials of the present invention may contain grooves orform grooves in combination with any other layer material, in order toform flow channels when put together with another similar electrodearray, or with simply another sheet material, for example, a plasticfilm.

Another method to create a flow channel is to use a separate flow spacer3 between electrode array sheets. Any membrane or spacer known to beused in reverse osmosis, flow-through capacitors, batteries, fuel cells,or capacitors can be used as an electrically-insulating layer and/or asa flow spacer 3 between electrode arrays.

Geometries which allow for anode-cathode pairs of electrodes 1 orelectrode material where the majority of the facing surface does notdirectly oppose the opposite polarity electrode 1 will form theelectrode array of the present invention. One way to achieve this is forthe electrodes to be coplanar. Anodes and cathodes may be coplanar inthe same sheet of material. Alternatively, electrodes 1 which comprise,at any one time, anodes or cathodes, which may be contained in differentsheets, separated by a spacer, while at the same time having less than50% of their facing areas directly opposing each other, according to thepresent invention. For example, electrodes 1 made as arrays of lines orother shapes may be made into separate anode and cathode sheets, whichmay be placed on top of each other and separated by a spacer layer. Theonly portion of these lines that would oppose each other would be whenthe lines or shapes intersect. More than 50% of the facing electrodeswould not be directly opposed to each other. In the case where anodesand cathodes are formed on the same sheet of material, the amount ofoverlap between separated sheets of materials does not matter. Whenelectrode array sheets containing both anodes and cathodes within thesame sheet-are layered, these array sheets may be electrically isolatedby means of an extra thick spacer, for example, over 0.001 inches thick,without increasing electrical resistance. The thick insulating spacer inthis case also serves as a means to contain electrolyte. However, unlikein the prior art, making this spacer thick in order to insulate onelayer from the next does not increase resistance. The resistance isgoverned by the space between the lines or shapes that form theelectrode array. Electrodes 1 formed as lines, strips, or rectanglesupon a flat nonconductive surface, with the widest capacitive surface ofthe electrode 1 in the same plane as the nonconductive spacer surface 2,will form a capacitor, battery, electrochemical cell, or anode-cathodepair or grouping or electrode array 7, according to the presentinvention. In this case, the electrodes 1 are also coplanar with thecurrent collector 6 and dielectric spacer 2. The capacitive surface orsurfaces of the electrodes 1 may also be perpendicular or offset fromthe plane of the spacer or spaced apart layers. For example, thecapacitance or electrochemical electrodes 1 may be formed asindentations, grooves, or sides of holes cut into an electrode material.

Any of the layers represented in FIGS. 1-8, including dielectric spacers2, flow spacers 3, insulators, electrodes 1, or current collectors 6 canbe manufactured by any of the following methods: extrusion, photomasking, photolithography, lithography, screen printing, intaglioprinting, stenciling, drawing, spraying, electroplating,electrostatically sticking, electrocoating, embossing, photo engraving,ink-jet printing, laser printing, off-set printing, contact printing,thermography, digital printing, gravure printing, as well as anyoptical, digital, photographic, light sensitive, or any other maskingtechnique known to be used in the coatings, printing, circuit board,optical, or semiconductor industry.

FIG. 9 depicts an alternative design of a flow-through capacitor orflow-through electrochemical cell utilizing the electrode array 7 of thepresent invention. Electrode array 7 is shown in FIG. 9 in aspiral-wound configuration, but may be any geometry of facing layerswith a flow path alongside or through the layers. As shown in FIG. 9,flow path 4 descends downward through electrode array 7, insidecartridge holder 11. A power supply 9 can supply electric power to theanode-cathode pairs of the electrode array 7. Pretreatment item 10 canoptionally be included in the electrochemical system of FIG. 9, asdetermined by one skilled in the art. Without limitation, in oneembodiment, pretreatment item 10 can be a source of an anti-foulantchemical, acid, or polyphosphate that is metered into the fluid feedstream when the cell is used as a flow-through capacitor, oralternatively only during the concentration-waste generating cycles ofoperations. Where used as a fuel cell, a fuel tank or source may beadded, and a storage battery or electrical load may be provided. Valve13 can be controlled by mechanisms known to those skilled in the art,such as a computer, a logical controller, a conductivity sensor, atimer, or a relay. Where the electrode array 7 is used in a flow-throughcapacitor, valve 13 can be a means of separating the waste product partof a flow-through capacitor cycle.

In additional alternative embodiments, the electrochemical system canfurther comprise an accumulation tank, and may be, for example, abladder tank. Cartridge holder 11 may be engineered so that thecartridge or electrode array 7 can be easily removed. An existingcartridge-cartridge holder combination common to the water filtrationindustry can be adapted for this purpose, as would be understood tothose skilled in the art. Any existing means of connecting a removeablebattery to a load while inside a device or cartridge may be duplicatedas a means of providing power to the cartridge or electrode array 7inside of the cartridge holder 11.

The electrode arrays of the invention can be prepared with the materialsdiscussed below.

Electrodes

The electrode material may be, without limitation, a fringe fieldelectrode, a carbonaceous material, a conductive polymer, ceramic, metalfilm, aluminum or tantalum with an oxide layer, metalized polymer orMYLAR®, a binder carbon mixture, a binder carbon powder mixture, apolytetrafluoroethylene (PTFE) carbon powder, PTFE carbon black, or PTFEactivated carbon mixture. One preferred embodiment is to use a carbonmaterial having a surface specific capacitance of about 5 microfaradsper square centimeter of electrode surface area, where single electrodecapacitances are measured in concentrated sulfuric acid or in 0.6 Msodium chloride (NaCl). The electrode surface area above refers to theinternal surface area of the electrode material, as measured by theB.E.T. or nitrogen absorption method.

Also useful as an electrode material of the invention are thosematerials that provide over 1 farad/cubic centimeter capacitance. Carbonis particularly advantageous, due to the fact that carbons may beselected for long life times, for example, over 1000 hours, while cyclecharging in 0.6 M NaCl. Forms of carbon that may be used include,without limitation, carbon black activated carbons, aerogels, reticlecarbons, nanotubes, high capacitance carbon blacks, alkali- andacid-activated carbons, carbon fibers, and carbons selected forresistance to oxidation.

Where it is desirable use an electrode material that includes a binder,various forms of binder may be used, including latex, polyolefins, PTFE,phenolic resin, and carbonized binders. Binders known to the art andused to bind carbon particles together in capacitors may be employed,including sintered organic binders. A particularly advantageous form ofbinder is a polyelectrolyte or polymer, either cross-linked ornoncross-linked, which forms a hydrogel in water. These include, but arenot limited to, polystyrene with ionic groups, including sulfonic acidand amine groups, strong acid groups, strong base groups, as well asweak acid or weak base, or a suitable group known to those skilled inthe art to be useful in ion exchange resins. Other binders that may beused include: cross-linked, acrylic acid; methylacrylic acid;acrylamide; acrylonitrile; melamine; urethane; acrylic, heat, orradiation curable polymers; epoxy; water absorbent polymers; andpolymers modified with crosslinks, ionic, or hydrophilic groups.Hydrophilic binders are preferred. Binders that occlude less than 50% ofthe B.E.T. measured surface area of the carbon particles are alsopreferred. The amount of cross-linking may be varied from between 0.1%and 75% in order to increase ion exchange capacity.

Additional polymers and manufacturing methods of forming a polymer layermay be used as a binder to form the carbon or other conductive materialtogether into electrodes for use in the present invention. See, Gray,Fiona M., Solid Polymer Electrolytes, VCH Publ., 1991. Amounts ofcross-linking may vary from 0% to 50% or more. Suitable carbon particleelectrode binding polymers include: polyethers, polyamides, polyacrylicacid, polyamines, polyvinyl alcohol, polyvinylcaprolactam, andvinylpyrrolidone polymers, as well as any homopolymers, copolymers,block, dendritic, cage, or star polymers, comb branched, network,random, or other polymer mixtures of the above.

U.S. Pat. No. 6,183,914 B1, issued Feb. 6, 2001, discloses apolymer-based conducting membrane. This material, as well as the priorart materials cited in this patent, may be mixed with carbon particlesto be used as a binder formulation used to manufacture electrodesaccording to the present invention. Polyelectrolytes may be usedtogether or combined with electrodes as described in PCT InternationalApplication No. US01/12641, entitled “Charge Barrier Flow-ThroughCapacitor.” These polyelectrolytes may, for example, be cross-linked orintertwined together so that the electrode does not swell more than 50%in water. The percent of cross-linking needed to achieve this may be 2%or more. Polyelectrolytes may be held together inside a differentnetwork polymer, particularly by selecting polymers or polyelectrolyteswith molecular weights above 1000. Block or copolymers may also be used.Polyelectrolytes may be derivatized, either before or prior toincorporation into the electrode, using any ionic group, chemistry, ormanufacturing method known to be used in ion exchange resins orpermselective membranes.

For use in integrated charge barriers, the hydrogel may have ionic orion exchange groups bound to it, as known to those skilled in the art.Without limitation, ionic groups described in the charge barrierflow-through capacitor of PCT International Application No. US01/12641may be used. These ionic groups may be fixed to a binder material or maybe fixed to a coating, membrane, polymer, or polyelectrolyte either as alayer on top of the electrolyte, infiltrated throughout the electrode,used to bind electrode material together, or fixed directly to thecarbon or other electrode material itself. The amount of cross-linkingmay be varied so that the ion exchange capacity of the hydrogelpolyelectrolyte binder may be above 0.1 milliequivalents per cubiccentimeter, for example, above milliequivalents per cubic centimeter, upto 4-7 or more milliequivalents per cubic centimeter. High ion exchangecapacity of over 0.1 cubic centimeter is advantageous to exclude ionsfrom the pores of the electrode due to Donnan Exclusion. Ionic groupsmay be selected from strong acid, strong base, weak acid, weak base,chelating, ion selective, or biologically selective groups, includingthe use of antibodies and enzymes fixed to the hydrogel binder.

In other embodiments, electrodes can be prepared from a carbon materialor carbon binder mixture currently used in electrochemical cells, asknown to those skilled in the art. In addition to the already citedexamples, this can include, without limitation to: polymer-graftedcarbon preparations, such as those described inhttp://ecl.web.psi.ch/Publications/Richner A00.pdf, and reticulatedcarbon, aerogel carbon, carbon fibers, nanotube carbons, activatedcarbons, carbon-hydrogel mixtures, suspensions of carbon binder mixturesformulated for use in coating processes, graphite, or any kind ofcarbon, in addition to other metallic, ceramic, polymeric, organic, orinorganic conductive materials. Optionally, any of these above materialsmay be mixed with a binder, sintered, or combined together in othercombinations.

Some electrochemical cells may beneficially require that alternateelectrodes be of different materials. For example, electrode arrays foruse in lithium ion batteries can be of alternating groups ofintercalating graphite electrodes and oxide electrodes such as, withoutlimitation, oxides of nickel, manganese, cobalt, or mixtures thereof.Solid polymer electrolytes, or other various electrolytes used in agiven electrochemical cell technology, can be used together with theelectrode array of the present invention.

Generally, electrochemical cell technology may be directly adapted tothe present invention by using their anode and cathode materials intothe anodes and cathode materials of the electrode array and using theirelectrolyte within or between electrode arrays, such as separated by afluid-containing space or spacer to contain the electrolyte. For generaluse in energy storage devices, such as lithium ion or electrochemicalbatteries, the electrodes of the present invention may be separated by aspacer whose purpose is not for flow, but to contain electrolyte. Flowspacers within the cell, together with a cartridge holder containinginlet and outlet means, may be added for fuel cells, flow-throughcapacitors, and other flow-through electrochemical cells. In eithercase, the electrolytes, electrode materials, and spacer materials usedin any prior art electrochemical cell may be used as electrolytes,electrodes, and fluid-containing spacers with the electrode array of thepresent invention.

Dielectric Spacer

The dielectric spacer used as an insulating material between theelectrodes may be a sheet of material of less than, for example, 0.1inches, preferably under 0.02 inches, for example, 0.0001-0.020 inch.The sheet may be of MYLAR®, polymer, plastic, or a nonporous or poroussheet material known to those skilled in the art. In some embodiments,the spacer may be prepared from a material that is an electric and ionicinsulator, that is electrically insulating but an ionic conductor, is amembrane, e.g., a NAFION® membrane (NAFION is a registered trademark ofE.I. Du Pont De Nemours and Company Corporation of Wilmington, Del.), amembrane of selective permeability, or a nonwoven, woven, ceramic, orother thin sheet material.

Current Collector

An optional current collector-layer may be used comprised of metal,titanium, or graphite foil or graphite coatings on a nonconductive film,or of a metal foil or film, a metallized polymer film, or of aconductive layer, such as a layer of conductive polymer or ceramicsubstrate. Foils or films under 0.1 cm thick are preferred, for example,0.02 cm or less thick. The current collector may either be coated on orembedded within the electrode, or, may serve as a flat substrate forelectrode or spacer layers.

Optional Flow Channel

Materials useful for forming a channel for the flow of fluids in aflow-through capacitor include those materials known to the art to besuitable as flow spacer in prior art flow-through electrochemical cells,including without limitation: netting, biplanar filtration netting,thermoplastic material, insect netting, nonwoven textile spacers,protrusions or bumps, and screen-printed pairs of offset lines. Flowchannels can be of a thickness chosen by one skilled in the art. Giventhat capacitance is formed within the electrode layer, flow channels maybe as thick or as thin as desired to optimize flow properties and tooptimize pressure, for example, to reduce any potential drop inpressure. Without limitation, pressures can be optimized at below 100psi, for example, 10 psi or less.

Any of the above layers may be laminated, glued, or formed together intoan integral composite material.

Numerous embodiments besides those mentioned herein will be readilyapparent to those skilled in the art and fall within the range and scopeof the invention. All references cited in this specification areincorporated by reference in their entirety. The following examplesillustrate the invention, but are in no way intended to limit theinvention.

EXAMPLE 1

A thin sheet electrode array, under 0.1 inches thick, preferably under0.02 inches thick, with alternating electrodes such as shown in FIG. 1or 2, is placed against a flow spacer. One or more electrode arraylayers are placed together with the flow spacer in any geometry used inflow-through capacitors or electrochemical cells. The electrode arrayand flow channel layers may be held together or compressed between endplates in order to form a flow-through electrochemical cell. Inlet andoutlet means are provided exactly as in any other parallel electrodeprior art electrochemical cell. The difference in the present inventionis that electrodes in any prior art electrochemical cell geometry arereplaced by electrode arrays of the present invention. A separate layerof current collectors may be placed underneath the electrode material.

EXAMPLE 2

Carbon powder PTFE electrodes of 0.01 inch thick are laminated with agraphite current collector layer and a 0.001-inch thick, nonporous,polymer spacer on one or both sides of the electrode/current collector.Arrays of holes 0.005 inches wide, spaced 0.010-inch center to center,are cut through spacer, electrode, and current collector layers in orderto form a thin sheet electrode array. This array may be spiral wound,stacked flat against, or laminated for use with a separator used to forma flow channel and formed into an electrochemical cell or flow-throughcapacitor of any prior art geometry, where the electrode array of thepresent invention replaces the electrode used in the prior art.

EXAMPLE 3

Carbon powder PTFE electrodes of 0.01 inch thick are laminated with agraphite current collector layer and a 0.001-inch thick, nonporous,polymer spacer on one or both sides of the electrode/current collector.This is subsequently stacked or rolled into a jelly roll and heattreated or glued together in order to bind the layers together into amonolith. The monolith may be a rectangle, or cylinder, or any othershape. The monolith is subsequently skived diagonally or perpendicularlyacross the layers in order to form thin electrode sheet arrays of thepresent invention for use in electrochemical cells or flow-throughcapacitors.

EXAMPLE 4

Arrays of conductive lines 0.003 inches thick, 0.0005 inches tall, andspaced apart 0.001 inches, are printed onto polymer or MYLAR® film inorder to form an electrode array of the present invention.

EXAMPLE 5

A carbon black binder mixture is screen-printed onto an insulatingspacer to form an array of lines 0.003 inches wide, 0.0005 inches tall,and spaced apart 0.001 inches. The spacer may be a polymer, porous, ornonporous, for example, MYLAR®, or a nonwoven porous polyolefin sheetmaterial, or a thin film of any polymer. Every other line extends outfurther than the next line. These lines may be connected in parallel byplacing a conductive strip down a side, back, and/or length of thealternating anodes on one side and the cathodes on the other side.Alternating the power supply means used to apply voltage to theelectrode lines may reverse polarity.

To form a current collector, a graphite or other conductive layer may beprinted or coated directly on top of the lines, in order to form aconductive layer.

EXAMPLE 6

Layers of electrode, insulating spacer, and optional current collectorare rolled into a jelly roll or into concentric circles. By use ofbinders, heat, calendars, coating, spraying or other means, these layersare formed into a composite that is subsequently skived or sliced into0.020 inch or less sheets, by cutting diagonally or perpendicularlyacross the layers. This forms electrode array sheets. These electrodearray sheets may be further layered or laminated with a flow spacer inorder to form a flow-through capacitor. The laminated electrode arraysmay be put together with additional spacers, porous spacers, ionconductive spacers, membrane spacers, nonwoven or woven or net spacers,screen-printed, open, or any other spacer means used in facinggeometries as in any other prior art flow-through capacitor orelectrochemical cell.

Flow may be through or preferably across the electrode array and throughthe flow space between the facing electrode arrays.

EXAMPLE 7

A laminate of alternating electrodes and spacers is formed by coating,spraying, electroplating, extrusion, or calendaring methods to form alog, rectangle, or cylinder which is subsequently cut into layers lessthan 0.5 inches thick, or which is extruded into thin sheets with theparallel laminations running across the width or the length of thesheet. Sheets may be less than 0.5 inches thick, for example, less than0.02 inches thick. Electrodes in this sheet may be thinly divided byinsulating spacer lines, less than 0.02 inches apart. Alternatingelectrodes or current collectors may be masked or insulated at the ends,so that a perpendicular connecting lead may connect alternate electrodeson each end to form anode/cathode pairs, as illustrated in FIG. 1.

EXAMPLE 8

A thin conductive film of graphite or polymer-backed graphite is paintedwith a photo resist masking chemical and illuminated through a patternto expose a series of lines 0.05 cm or less wide and 0.05 cm or lessapart. Upon washing, a pattern of grooves is revealed exposing theunderlying current collector material. A carbon black material of over500 BET is mixed with a 5% or more cross-linked, strong polyelectrolyteor hydrogel binder containing strong acid or strong base groups, or,alternatively, is mixed with any other binder to form a slurry. Thisslurry is wiped, sprayed, or coated onto the current collector/photoresist layer. Any excess is wiped off, revealing an alternating patternof electrode and insulating material lines. This carbon binder mixturemay be cross-linked, dried, or solidified by temperature, or by light,catalysts, time, or other methods. Two of these identical sheets may besandwiched together with a flow spacer and manufactured to form aflow-through capacitor according to any prior art flow through capacitorgeometry, such as those described in Andelman U.S. Pat. No. 5,192,432,issued Mar. 9, 1993; U.S. Pat. No. 5,196,115, issued Mar. 23, 1993; U.S.Pat. No. 5,200,068, issued Apr. 6, 1993; U.S. Pat. No. 5,360,540, Nov.1, 1994; U.S. Pat. No. 5,415,768, issued May 16, 1995; U.S. Pat. No.5,547,581, issued Aug. 20, 1996; U.S. Pat. No. 5,620,597, issued Apr.15, 1997; U.S. Pat. No. 5,748,437, issued May 5, 1998; U.S. Pat. No.5,779,891, issued Jul. 14, 1998; or in Otowa U.S. Pat. No. 5,538,611,issued Jul. 23, 1996; or in Andelman PCT International Application No.US01/12641, “Charge Barrier Flow-Through Capacitor.” Alternatively, alllayers may be screen-printed. Electrode or spacer layers may be made asprotruding ridges in order to form flow channels when two electrodearrays are placed together in an opposing manner, with the sets of linesoffset at an angle from each other.

EXAMPLE 9

The electrode array of the present invention may require the manufactureof patterned thin films of materials in juxtaposition to each other,layered together, or on top of each other. A particularly useful methodto do this is to use electrostatic or other self assembly methods, suchas those described in U.S. Pat. No. 6,316,084, issued Nov. 13, 2001, andU.S. Pat. No. 6,291,266, issued Sep. 18, 2001, and Spillman Jr., et al.U.S. Patent Application Publication No. 20020037383A1, published Mar.28, 2002, each of which is hereby incorporated by reference. Thesemethods can be used to manufacture the electrodes, spacers, and currentcollectors of the present invention. Electrostatic powder coatingtechnology can also be used to form the electrode, current collector,insulating spacer, and flow spacer layers. Especially where electrodesare dots or shapes other than lines, and need to be connected in groupsof anodes and cathodes, technology such as described in U.S. Pat. No.5,070,036, issued Dec. 3, 1991, and U.S. Pat. No. 4,977,440, issued Dec.11, 1990, can be used to form interconnecting groups of currentcollectors.

1. An electrode array for use in an electrochemical cell, said arraycomprising: a) substrate; and b) at least one pair of electrodes on saidsubstrate, wherein each of said electrodes has a facing surface having afacing surface area and a nonfacing surface having a nonfacing surfacearea, said facing surface area being smaller than said nonfacing surfacearea, and wherein the facing surfaces of each said pair of electrodesare separated by a dielectric material.
 2. A sheet material containingthe electrode array of claim
 1. 3. The sheet material of claim 2,wherein one electrode of said pair is an anode and the other electrodeof said pair is a cathode.
 4. An electrochemical cell consisting of thesheet material of claim
 3. 5. The sheet material of claim 4, whereinsaid sheet material is wound in a spiral.
 6. The electrode array ofclaim 1, wherein said substrate is a planar sheet material, and saidelectrodes are coplanar.
 7. The electrode array of claim 2, where saidpair of electrodes are made from a carbon material.
 8. The electrodearray of claim 1, wherein said electrode array has a series resistanceof less than 50 ohms/cm² of electrode array facing area, and anelectrical leakage resistance of more than 30 ohms/cm² of electrodearray facing area.
 9. The electrode array of claim 1, wherein thenonfacing surfaces of each pair of electrodes are separated by adistance of less than 3 millimeters.
 10. The electrode array of claim 1,wherein the facing surfaces of each pair of electrodes are separated bya distance of more than 0.002 centimeters.
 11. The electrode array ofclaim 1, wherein each of said electrodes in said electrode pair has aconcentric spiral shape.
 12. The electrode array of claim 1, whereineach of said electrodes has a surface area of greater than 10 m²/gramB.E.T.
 13. A flow-through capacitor comprising the electrode array ofclaim
 1. 14. The flow-through capacitor of claim 13, further comprisinga fluid flow path for the passage of a fluid across the surface of saidarray.
 15. A flow-through capacitor comprising the electrode array ofclaim 6 and a flow path for the passage of a fluid across the nonfacingsurfaces of the electrodes in said array.
 16. The flow-through capacitorof claim 15, wherein said flow path comprises a porous,nonelectrically-insulating material.
 17. A flow-through capacitorcomprising: a) at least two electrode arrays of claim 6; and b) a flowpath for the passage of a fluid across the nonfacing surfaces of theelectrodes in said array, said flow path having a thickness of at least20 micrometers in thickness.
 18. A method of lowering the seriesresistance of an electrochemical cell, comprising the steps of: a)providing an electrode array, said array comprising a planar substrateand at least one pair of electrodes on said planar substrate, whereineach of said electrodes has a facing surface area and a nonfacingsurface area, said facing surface area being smaller than said nonfacingsurface area, and wherein the facing surface areas of each pair ofelectrodes are separated by a dielectric material; and b) inserting saidelectrode array into said electrochemical cell.
 19. The method of claim18, wherein said electrochemical cell is a flow-through capacitor. 20.The method of claim 18, wherein said electrochemical cell is a lithiumbattery.